I. Field of the Invention
This invention relates generally to metal working machines, and more particularly to a portable boring bar assembly that can be used to rebore cylindrical apertures and/or reface flange surfaces such as may be found on valves and other pipe or casing fittings in the field, and which is simple and quick to install and operate.
II. Discussion of the Prior Art
Portable boring bars are known in the art. They generally consists of an elongated, cylindrical bar having a tool bit mounted thereon where the cylindrical bar is journaled for rotation in a frame attachable to the work piece. A first drive member may be used to rotate the bar and a second drive member provides axial feed to the bar and the first drive member. See, for example, the York U.S. Pat. No. 4,932,814, the Flaten U.S. Pat. No. 4,573,837, and the Sverdlin U.S. Pat. No. 4,652,186.
In the York ""814 patent, there is described an arrangement in which a cylindrical boring bar is journaled for rotation in a pair of supports, one of which is axially movable via a lead screw and is adapted to translate the boring bar and its rotary drive motor assembly. A boring tool is mounted along the length of the boring bar and projects radially there from for engaging the wall of a cylindrical bore to be refurbished.
It is to be noted that in the York machine, the source of rotational power for the boring bar can only be attached to one end of the boring bar and, likewise, the drive motor for the axial displacement of the boring bar can only be located at one end of the feed screw utilized. These constraints may render the York machine unusable in a variety of situations encountered in the field where obstructing structures get in the way of placement of the machine relative to a particular work piece to be refurbished. A much more facile machine results where the mechanism for rotating the boring bar as well as the drive for translating the cutting head can be adjustably positioned any where along the length of the boring bar.
Properly aligning the boring bar of the York ""814 patent with the central axis of the bore of the work piece to be refurbished may also prove difficult. As is explained in that patent, the boring bar 12 is passed through the bore of the work piece and bearing collars 42 and 44 are assembled onto opposite ends of the boring bar and advance therealong until the work piece is sandwiched between the bearing collars. At this point, the boring bar must be manipulated to align it properly within the bore of the work piece, whereupon the bearing collars 42 and 44 are welded to the work piece. In practice, the alignment of the boring bar with the axis of the bore of the work piece would be difficult and time consuming
It is accordingly one object of the present invention to provide a portable boring/facing machine incorporating a boring bar with first and second drive mechanisms that are positionable theoretically at an infinite number of locations along the length of the boring bar rather than being confined to an end thereof.
A further object of the invention is to provide a portable boring/facing machine having a boring bar mounting arrangement that simplifies the alignment process.
Another object of the invention is to provide a portable boring/facing machine where the boring bar is adapted to be driven via gear box transmission, thereby increasing the torque available as compared to a directly driven boring bar.
Another object of the invention is to provide an accessory cutting head member adapted to be assembled onto a boring bar and providing radially displacement of a cutting tool for use in facing operations.
A still further object of the invention is to provide a portable boring bar machine having precise control over the feed rate of a cutting tool relative to the work piece being refurbished.
The foregoing objects and advantages are realized by the present invention in which a boring/facing machine comprises an elongated, generally cylindrical, rigid boring bar member that is journaled for rotation in a pair of spaced-apart mounting brackets attachable to the work piece to be refurbished. The mounting brackets each have a bore with an internal concave spherical surface that cooperates with an external convex spherical surface of a bearing retainer member. The bearing retainer member of each mounting bracket contains a set of bearings for journaling the boring bar member. Because of the cooperation of the spherical surfaces in the bore of the mounting brackets and on the bearing retainers, centering an alignment of the boring bar with a central axis of the work piece to be machined is facilitated.
The boring bar supports a cutting head member thereon which rotates with the boring bar when a first drive motor is activated. A second drive motor provides axial (longitudinal) translation of the cutting head member.
In accordance with a first embodiment, the axial translation of the cutting head is along the length of the boring bar and is achieved by using a lead screw powered by the second drive motor, the lead screw being journaled for rotation within a channel or groove in the surface of the boring bar. The lead screw carries a traveling nut that engages the cutting head member.
In a second embodiment, the cutting head member is positionable along but fixed in place at a predetermined location on the boring bar member at the time of set-up, and the boring bar, with the cutting head member, is axially translated, again using a lead screw driven by the second drive motor.
In either embodiment, the cutting head member may comprise a boring tool support when a cylindrical wall surface of the work piece is to be rebored or, alternatively, may provide radial movement of a cutting tool in the case of a refacing operation.
In either of the aforementioned two embodiments, the first drive motor is indirectly coupled to the boring bar via a gear box that is positionable at a selectable location along the length of the boring bar. Also, the lead screw is arranged to be driven by a variable speed servo motor, whereby the longitudinal feed of the cutting head member can be precisely controlled by adjusting the voltage applied to the servo drive motor.